1. Field of the Invention
This invention relates to a process for catalytic decomposition (cracking) followed by hydrogenation of high molecular weight hydrocarbons to produce lower molecular weight hydrocarbon products in both surface and subsurface applications at ambient temperatures and pressure with no CO or CO2 emissions.
This invention further pertains to the separation of inorganic solids, sands, clays, etc., from hydrocarbon compound substrates and mixtures or sludge derived from an originating petroleum source, subsurface or surface, or in the form of petroleum contaminated waste.
This invention also pertains to the complete or partial desulfurization by reduction of the sulfur-containing species.
This invention also pertains to the remediation of soils by the removal of hydrocarbon contaminants.
2. Description of Related Art/Prior Art
The generally accepted concept of the origination of oil and gas is that it was generated from the thermal degradation of kerogen, a fossilized material in shale and other sedimentary rock that yields oil upon heating. It is the most common source of carbon in the earth's crust. The major factors affecting the concentration of petroleum are the chemical nature of the kerogen, temperature, time, mineral composition, resident geological structure, etc.
Traditional technology for cracking and hydrogenation, such as catalytically cracking hydrocarbon, serve to form more valuable lower molecular weight products. Hydrocracking reactions between the initial hydrocarbon substrate and the catalytic agent may be carried out in a series of bed reactors or in a distillation column. Such reactions are endothermic and, as such, the reactors must be heated. Additionally, hydrogen is recycled through the system to ensure maximum hydrocarbon saturation to form the lower molecular weight hydrocarbon products and to remove excess hydrogen generated by the catalytic reaction. In these systems, polyaromatic rings are also opened and the by-products hydrogenated.
Substantial quantities of petroleum in the earth have proven difficult or impossible to recover because they are in the form of high molecular weight hydrocarbon mixtures which are distributed and intermixed in tar sands, shale, and various rock formations. Furthermore, hydrocarbon compounds cannot be economically extracted from “depleted” oil wells because they are not sufficiently concentrated to be extractable by drilling, have lost their original gas pressure, and/or have relatively high density and viscosity at the given location. The latter compounds will not flow unless heat energy is applied to the petroleum deposit, as, for example, by steam. Additionally, once extracted, these materials still require heat energy to remain as liquids and may be contaminated. Waste or contaminated materials (e.g., soil, rock, sludge, oil tars) containing hydrocarbons, crude or refined, cannot be economically extracted from naturally or man-made contaminated materials.
There are well known enhanced production techniques to obtain oil from depleted or under-producing wells. In situ combustion is a technique used to heat crude petroleum materials below the surface of the earth to reduce their viscosity. An oxidizing agent, such as air, is injected into the subsurface deposit at sufficiently high temperatures to initiate a combustion process or a phosphorous bomb or gas burner is lowered into the well. The lower molecular weight hydrocarbons generated then rise to the surface of the deposit. There are drawbacks to this procedure in that the high temperatures necessary for combustion, combined with the presence of oxygen, lead to undesirable side reactions of coking and the formation of phenols and ketones, which are difficult to process through other refining techniques.
Thermal recovery techniques from under-producing, depleted, and heavy oil wells and bitumen deposits may also comprise steam injection. The purpose of the injected steam is to heat the heavy hydrocarbon deposit, thereby significantly reducing the viscosity and making an economically acceptable level of recovery of the hydrocarbon deposit. In situ hydrovisbreaking and steam flooding are alternatives to the combustive techniques. Sometimes, in this process, a catalyst is suspended in the steam and circulated throughout a subsurface deposit. This heat permits the endothermic reaction to occur, causing lower molecular weight hydrocarbons rise to the surface of the petroleum deposit. This process may only be used in formations that have sufficient overburden thicknesses to withstand the injection of high temperature, high pressure materials.
Waterflooding techniques are also a frequently employed method to improve oil recovery from depleted or nearly depleted oil wells and can be expected to yield between 5% and 50% of the remaining petroleum products. The water to be injected must first be filtered to eliminate all potentially reactive particles. Then it is pumped into the well under pressure either from a group of strategically placed injection wells or from injection wells at the edge of the oilfield. Water rarely circulates evenly through the underground deposits. In most cases, the water permeates the deposits until it causes a breakthrough, creating a path of least resistance to the producing well along which the water will flow. The oil has a lower specific gravity than water and floats on top of the water. Such waterfloods are most effective in areas where there is little primary production. Variants of this technique include alkaline or caustic flooding, which involve the addition of basic agents to the water, such as sodium hydroxide.
Miscible gas drive for enhanced oil recovery involves injecting an inert gas, such as carbon dioxide, nitrogen, or liquefied petroleum gas into the reservoir. The gas mixes with the petroleum deposits, making the oil less viscous, and pressures the fluid oil towards the producing well. Sometimes alternating between pumping gas and water through the well is employed. Solvent or chemical flooding comprises injecting a liquid with different chemicals in batches (slugs) into a deposit. A micellar-polymer flood will contain a polymeric surfactant to wash reservoir pore spaces clean of the heavy oils present within the earth formation. Other solvents can be used to mix with and reduce the viscosity of the petroleum deposits. Frequently used solvents include aromatic hydrocarbons, carbon disulfide, and carbon tetrafluoride, which are all capable of dissolving bituminous petroleum deposits. Water-based solvents have been used, with both heated and unheated water, to carry active ingredients throughout subsurface formations. Solvents or chemicals are frequently pumped through pipelines along with the treated oil. These must be separated out, e.g., by distillation to preserve both expensive solvents and the treated oil. Elimination of this refining step would reduce complications and cost.
It can be relatively difficult and economically unfeasible to separate hydrocarbon compound mixtures from some of the inorganic solid materials that are naturally intermixed.